Apparatus for delivering a breath sample to a solid state sensor

(19)

(11)

EP 0 327 396 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	17.10.1990 Bulletin 1990/42

(43)	Date of publication A2:
	09.08.1989 Bulletin 1989/32

(21)	Application number: 89301100.7

(22)	Date of filing: 03.02.1989

(51)	International Patent Classification (IPC)⁴: G01N 33/48

(84)	Designated Contracting States:
	DE ES FR GB IT

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Priority:

05.02.1988 US 152470

(71)	Applicant: GUARDIAN TECHNOLOGIES, INC.
	Denver Colorado 80203 (US)

(72)	Inventors:
	Comeau, Felix J. E. Brampton Ontario (CA) Kupferschmidt, Gerald J. Oakville, Ontario (CA) Read, Richard E. Blanchester, Ohio (US)

(74)	Representative: Allen, Oliver John Richard et al
	Lloyd Wise, Tregear & Co., Commonwealth House, 1-19 New Oxford Street London WC1A 1LW London WC1A 1LW (GB)

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References cited: :

(54)	Apparatus for delivering a breath sample to a solid state sensor

(57) An apparatus for delivering a gas sample such as a breath sample to a solid state sensor operating to sense the concentration of a constituent of the sample such as alcohol while the sensor is maintained within a predetermined temperature range is disclosed. The sensor is disposed within a sensor chamber (46) which communicates by way of a small bleed passageway (106) with a second chamber (102) formed in a conduit (6) having an inlet upstream of the second chamber and an exhaust downstream thereof. The pressure within the second chamber is passively regulated to lie within a predetermined range over an expected range of inlet pressures. This regulation is accomplished by means of flow restrictors disposed between the second chamber and its inlet and exhaust and results in a bleed flow to the sensor through the bleed passageway which is sufficient to ensure an accurate reading within a predetermined sampling interval while further ensuring that the bleed flow does not cool the sensor below its operating temperature range. The lower end of the pressure range at which the second chamber is regulated is selected to correspond to a minimum flow sufficient to provide a deep lung breath sample when that minimum flow is continued with out interruption for a period at least equal to a predetermined sampling interval. This minimum flow can be sensed for example by a pressure sensor operatively disposed in communication with the second chamber. To ensure that the pressure sensor cannot indicate the presence of the minimum flow when the exhaust is blocked, the invention further contemplates connecting the pressure sensor differentially across one of the flow restrictors separating the second chamber from its inlet and exhaust.

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